At present, in the field of the shoe factory machines that execute the pre-lasting and lasting of shoes, the cementing of the vamp sides to the insole is carried out by means of particular devices for applying thermoplastic cement.
These devices of the known type substantially consist of sensing and cement-applying feet under which the insole along the perimeter edge of which cement must be spread, is advanced.
Said cement-applying feet are fastened to the base of heater units adapted to fluidize a thermoplastic thread which is caused to pass therethrough. These units, together with their respective cement-applying feet, are mounted by pairs on the pre-lasting and lasting machines and are supported by arms that are reciprocally connected to each other at one end thereof by means of a pin, so that they can be independent in their respective movements. In this way, when an insole shaped on a last is caused to pass under said feet, the application of cement takes place uniformly as feet follow the differences in height of the last and always contact the insole. In practical applications, however, it often happens that, when the difference in height between one part of the last and the other is remarkable, for example in the case of woman shoes, this continuity of contact between the cement-applying feet and the insole ceases and, as a result, there is an irregular delivery of thermoplastic cement. More particularly, while the contact between the insole and the foot is always constant on the higher part of the last and therefore the delivery of cement can take place regularly, on the lower part the contact between the foot and the insole is not continuous and therefore along this part some areas will have an overamount of cement and other areas an insufficient amount thereof or even no cement at all.